There was a time, believe it or not, when Rascal Flatts was considered cutting-edge country.

Okay, "cutting-edge" might be pushing it — the trio’s wholesome, harmony-laden style was never all that controversial. Still, when you survey the pop- and R&B-infused sounds coming out of Nashville today, it’s funny to think of Rascal Flatts as the new kids on the block.

"We got absolutely blasted for having the guitars too loud in our stuff 20 years ago," Jay DeMarcus, the group’s founding bassist, said by phone recently. "Now there seems to be no limit to what you’re able to do. I’m proud that we’ve evolved to that point, but now, some of the criticisms that we got early on in our career seem like a joke to me."

Twenty years later, they’ve gotten the last laugh. With more than a dozen No. 1 hits like Bless the Broken Road and What Hurts the Most, Rascal Flatts remain one of Nashville’s most reliable headliners; their summer tour hits Tampa’s MidFlorida Credit Union Amphitheatre on Friday.

But two decades in, the trio — DeMarcus, guitarist Joe Don Rooney and inimitable high tenor Gary LeVox — feels they can still evolve. This decade, they’ve collaborated with Justin Bieber, Lionel Richie and Chris Stapleton, and they’re working on a covers album that DeMarcus said sounds like "something we’ve never done before."

"We’ve gone into the studio and recorded some of our favorite cover tunes that we grew up listening to," he said, "and I think people are going to be surprised by the covers that we’ve chosen."

Here’s more of what DeMarcus said about touring, opening acts and LeVox’s ageless voice.

I think eligibility for the Country Music Hall of Fame is 20 years after your first record. Is that something you’ve ever talked about?

Never really have. There are many times we feel like we’re just getting started and we have so much left to do. So it leaves us very little time to take a deep breath and look back on what we’ve done. It would be nice to happen someday, but who knows? It’s weird to think about being introduced as "Hall of Fame members Rascal Flatts."

It feels like something that should happen at the end, right? Like a career-capper, not a mid-career thing.

Like, posthumously. (laughs)

Left to your own devices, would you rather be out on a big summer tour, or hanging out at home in a studio?

I love both, and we are doing both right now. We’re working on some new music, so on our days off, we’re in the recording studio, and it’s the perfect balance. I’ve been on the road since I was 15, in one way or another — on a bus, in a 15-passenger van, pulling a U-haul — so I would be lying if I said sometimes the miles and the road didn’t get long. But it’s always rewarding, that hour and a half every night you get to stand up there and see it all pay off, and feel the love from that crowd.

Have there been shows where one of you has been sick and you’ve had to find somebody who could attempt to handle your harmonies?

We’ve never been in a place where somebody couldn’t croak out and limp through a night. We’ve canceled, in 19 years, maybe six shows that I can count off the top of my head, and that’s only because Gary couldn’t even talk. When you pull into a place and your lead singer can’t even complete a sentence, you’re in trouble.

How long can Gary keep singing in that register?

Gary’s an extraordinary singer and an example of somebody who’s a natural first tenor. He sort of talks there; he lives in that range all day long. He’s like Vince Gill. Vince Gill talks high, he lives there, he’s doing it with the Eagles, and he’s done it for 30 years. For Gary, it’s just, take care of what you got, be a good steward for it, and he’ll continue to perform at a high level for a very, very long time.

A decade ago, Taylor Swift opened for you guys. Before that, Jason Aldean and Blake Shelton. What’s it like to see your openers go on to become massive, global A-listers?

What it does for me is make me wish that we had run a record label and signed them all because our guesses were pretty good. That’s what you try to do — you try to pick the next crop of people coming up you feel are going to do something great. One thing I’m proud of is we’ve had a really good track record on picking those acts that have gone on to be bigger than we are.